Metal Gear Solid

Add '-cheatenable' into command line of the game (mgsi.exe -cheatenable) and use the following keys in game:

F2 -Hidden Ghosts
Those crazy developers who created this masterpiece have hidden pictures of themselves in the game. There are are total of 48 of them, all of which you can see when you snap a picture of a certain area when you play through the game a 2nd time. Here are the locations for all Spirit photos:

F6 - Snake in a Tux
If you want to play through the game with Snake in a tux, and the Ninja in red armor, 1st get both the Bandana and Stealth Suit. When you play through the game a 3rd time, Snake will change into the tux during the elevator sequence.

F7 - Infinite Ammo
Win the game without submitting to Ocelot when being tortured to save Meryl. There should be a new saved game. Load it and you will start out with a bandana. Wear it and you will get infinite ammo.

Win the game 2 times and get both the bandana and stealth camouflage. At the 3rd time of playing, reach up to the area where you fight Ninja without using the bandana or stealth camouflage. If done correctly, Ninja will be wearing red instead of blue. There will now be new textures for Snake and Ninja and new bonus music during the ending

Beat the game with submitting to Ocelot when being tortured to get Meryl killed.
There should be a new saved game. Load it and you will start out with a sleath
camouflage. Wear it and you will get invisibility.

Use the following steps to get both the Stealth Gear and Bandana. When you
complete the game by not submitting to the torture, you will only get the
bandana. Simply submit to the torture to get both items.

Successfully complete the game two times and get both the bandana and stealth
camouflage. At the third time of playing, reach up to the area where you fight
Ninja without using the bandana or stealth camouflage. If done correctly, Ninja
will be wearing red instead of blue. There will now be new textures for Snake
and Ninja and new bonus music during the ending Alternate costumes:

Successfully complete the game, wait until the credits end, and save the game.
Load the saved game file and play through the game again. After successfully
completing the game a second time, wait until the credits end, and save the
game. Load the saved game and play through the game again. Snake will change
into a tuxedo in the elevator during this game.

Reach area B2 of the tank hanger. At the end of the hallway to the right of
the door where you fight revolver is a secret room that is entered after using
C4 explosive. In the room are card 4 and card 6 doors. The camera is in the
room behind the card 4 door. Use the camera to take pictures to see various
extras, such as the faces of the development team.

Win the game with submitting to Ocelot when being tortured to get Meryl killed. There should be a new saved game. Load it and you will start out with a sleath camouflage. Wear it and you will get infinite ammo.

When you find Meryl on patrol in the office, she runs to the women's bathroom.
Follow Meryl into the Women's bathroom and reach the last stall in under five
seconds. Meryl will be caught with her pants down during an FMV sequence. Look
in the vent just before the DARPA chief (Decoy Octopus) to see Meryl doing
sit-ups. Leave the vent and re-enter and she will be doing one-armed pushups.
Repeat and she will be doing leg stretches on the wall. Repeat one more time
and she will be doing the leg stretches while pantless.